SEMICONDUCTOR STORAGE DEVICE

• US 20100295112A1
• Filed: 03/11/2010
• Published: 11/25/2010
• Est. Priority Date: 05/21/2009
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Aoki, Nobutoshi, Izumida, Takashi, Kondo, Masaki, Kanemura, Takahisa
• Granted Patent: US 8,212,306 B2
• Time in Patent Office: Days
• US Class Current: 257/316
• CPC Class Codes: H01L 29/40114 the electrodes comprising a conductor-insulator-conductor-insulator-semiconductor structure
• CPC Class Codes: H01L 29/42324 Gate electrodes for transistors with a floating gate
• CPC Class Codes: H01L 29/66825 with a floating gate H01L29/6684 takes precedence
• CPC Class Codes: H01L 29/7883 charging by tunnelling of carriers, e.g. Fowler-Nordheim tunnelling
• CPC Class Codes: H10B 41/30 characterised by the memory core region

Abstract

A semiconductor storage device has a semiconductor substrate, a plurality of first insulating films formed on the semiconductor substrate with predetermined spacing therebetween, an element isolation region formed between the first insulating films in a first direction, a floating gate electrode comprising a first charge accumulation film formed on the first insulating film, a second charge accumulation film formed on the first charge accumulation film and having a width in a second direction orthogonal to the first direction smaller than the width of the first charge accumulation film, and a third charge accumulation film formed on the second charge accumulation film and having the width in the second direction larger than the width of the second charge accumulation film, a second insulating film formed on the second charge accumulation film and between the second charge accumulation film and the element isolation region, a third insulating film formed on the charge accumulation film and the element isolation region along the second direction, and a control gate electrode formed on the third insulating film.

Claims

1. A semiconductor storage device comprising:

a semiconductor substrate;

a plurality of first insulating films formed on the semiconductor substrate with predetermined spacing therebetween;

an element isolation region formed between the first insulating films in a first direction;

a floating gate electrode comprising a first charge accumulation film formed on the first insulating film, a second charge accumulation film formed on the first charge accumulation film and having a width in a second direction orthogonal to the first direction smaller than the width of the first charge accumulation film, and a third charge accumulation film formed on the second charge accumulation film and having the width in the second direction larger than the width of the second charge accumulation film;

a second insulating film formed on the second charge accumulation film and between the second charge accumulation film and the element isolation region;

a third insulating film formed on the charge accumulation film and the element isolation region along the second direction; and

a control gate electrode formed on the third insulating film.

2. The semiconductor storage device according to claim 1, wherein the width of the second charge accumulation film in the first direction is smaller than each of the width of the first charge accumulation film and the width of the third charge accumulation film in the first direction.

3. The semiconductor storage device according to claim 1, wherein the width of the third charge accumulation film in the second direction is larger than the width of the first charge accumulation film in the second direction.

4. The semiconductor storage device according to claim 2, wherein the width of the third charge accumulation film in the second direction is larger than the width of the first charge accumulation film in the second direction.

5. The semiconductor storage device according to claim 1, wherein the second insulating film contains a material obtained by oxidizing the second charge accumulation film.

6. The semiconductor storage device according to claim 1, wherein the second insulating film contains the same material as the element isolation region.

7. The semiconductor storage device according to claim 2, wherein the second insulating film contains the same material as the element isolation region.

8. The semiconductor storage device according to claim 3, wherein the second insulating film contains the same material as the element isolation region.

9. The semiconductor storage device according to claim 1, wherein a top surface of the element isolation region is lower than the top surface of the third charge accumulation film.

10. The semiconductor storage device according to claim 1,

wherein the floating gate electrode further comprises fourth through (2n+1)'"'"'th charge accumulation films sequentially formed on the third charge accumulation film, where n is an integer not smaller than 2,

the width of the i'"'"'th charge accumulation film in the second direction is the same as the width of the second charge accumulation film, where i is an even number satisfying a relationship of 4≦

i≦

2n,

and wherein the width of the j'"'"'th charge accumulation film in the second direction is the same as the width of the first charge accumulation film, where j is an odd number satisfying the relationship of 5≦

j≦

2n+1.

11. The semiconductor storage device according to claim 1, wherein the first direction is parallel to word lines and the second direction is parallel to bit lines.

12. The semiconductor storage device according to claim 2, wherein the first direction is parallel to word lines and the second direction is parallel to bit lines.

13. The semiconductor storage device according to claim 3, wherein the first direction is parallel to word lines and the second direction is parallel to bit lines.

14. A semiconductor storage device comprising:

a semiconductor substrate;

a plurality of first insulating films formed on the semiconductor substrate with predetermined spacing therebetween;

an element isolation region formed between the first insulating films in a first direction;

a floating gate electrode comprising a first charge accumulation film formed on the first insulating film, a second charge accumulation film having a width in a second direction orthogonal to the first direction smaller than the width of the first charge accumulation film and formed on the first charge accumulation film so that a cavity may be formed between this second charge accumulation film and the element isolation region, and a third charge accumulation film formed on the second charge accumulation film and having the width in the second direction larger than the width of the second charge accumulation film;

a second insulating film formed on the floating gate electrode and the element isolation region along the second direction; and

a control gate electrode formed on the second insulating film.

15. The semiconductor storage device according to claim 14,

wherein the width of the second charge accumulation film in the first direction is smaller than each of the width of the first charge accumulation film and the width of the third charge accumulation film in the first direction,

and wherein a third insulating film is further comprised which is formed on a side portion of the floating gate electrode in the first direction so that a cavity may be formed between this third insulating film and the second charge accumulation film.

16. The semiconductor storage device according to claim 14, wherein a top surface of the element isolation region is lower than the top surface of the third charge accumulation film.

17. The semiconductor storage device according to claim 14, wherein the first direction is parallel to word lines and the second direction is parallel to bit lines.

18. The semiconductor storage device according to claim 15, wherein the first direction is parallel to word lines and the second direction is parallel to bit lines.